A third hearing in the trial of jailed Washington Post correspondent Jason Rezaian on espionage charges took place behind closed doors in Tehran on Monday, Iran's official IRNA news agency reported.

The first and second hearings of Iranian-U.S. citizen Rezaian were held behind closed doors on May 26 and June 8 respectively at the Revolutionary Court in Tehran. Rezaian has been in Tehran's Evin prison since his arrest in July 2014.

"The trial will continue and when the verdict is issued we will announce it to people," judiciary spokesman Gholamhossein Mohseni Ejei said, according to the semi-official ILNA agency.

U.S. President Barack Obama in March urged Iran's government to release Rezaian and two other detained Americans - Saeed Abedini and Amir Hekmati - and to help find Robert Levinson, an American who disappeared in Iran eight years ago.

Iran and the United States have no direct diplomatic relations, hampering efforts to free the detainees. Ties were cut following the 1979 Islamic revolution.

Rezaian's lawyer, Leila Ahsan, told Tasnim news agency in May after the first hearing that he had been charged with espionage for collecting confidential information, handing it to hostile governments, writing a letter to Obama, and acting against national security.

Rezaian's wife Yeganeh Salehi and a woman photojournalist who were detained with him but later released also went on trial last month, Iranian media reported.

Washington has rejected the espionage charges against Rezaian as "absurd". His brother Ali told Reuters Television in May that Rezaian, the Post's Tehran bureau chief, had lost 40 pounds (18 kg) in prison.

Tehran and six world powers, including the United States, are trying to meet a deadline later on Monday for a final nuclear deal to end a decade-old standoff with the West.